✨ add support for gcloud service accounts and private calendars

.env.example

@@ -2,4 +2,5 @@ DISCORD_EVENTS_SYNC_DISCORD_GUILD_ID=
 DISCORD_EVENTS_SYNC_DISCORD_BOT_TOKEN=
 DISCORD_EVENTS_SYNC_DISCORD_APPLICATION_ID=
 DISCORD_EVENTS_SYNC_GOOGLE_CALENDAR_CALENDAR_ID=
-DISCORD_EVENTS_SYNC_GOOGLE_CALENDAR_API_KEY=
+DISCORD_EVENTS_SYNC_GOOGLE_CALENDAR_API_KEY=
+DISCORD_EVENTS_SYNC_GOOGLE_CALENDAR_SERVICE_ACCOUNT_KEY_JSON=

.github/workflows/sync.yml → .github/workflows/calsync.yml

@@ -7,9 +7,9 @@ on:
   workflow_dispatch:
 
 jobs:
-  build:
+  calsync:
     runs-on: ubuntu-latest
-    name: sync
+    name: 🔁 Sync Events
     steps:
       - uses: acm-uic/calsync@main
         with:
@@ -18,3 +18,4 @@ jobs:
           discord-application-id: ${{ secrets.DISCORD_EVENTS_SYNC_DISCORD_APPLICATION_ID }}
           google-calendar-id: ${{ secrets.DISCORD_EVENTS_SYNC_GOOGLE_CALENDAR_CALENDAR_ID }}
           google-api-key: ${{ secrets.DISCORD_EVENTS_SYNC_GOOGLE_CALENDAR_API_KEY }}
+          google-service-account-key-json: ${{ secrets.DISCORD_EVENTS_SYNC_GOOGLE_CALENDAR_SERVICE_ACCOUNT_KEY_JSON }}

README.md

@@ -29,7 +29,8 @@ jobs:
           discord-bot-token: ${{ secrets.DISCORD_BOT_TOKEN }} # needs "bot" scope and "View Channels", "Manage Events", "Create Events" bot permissions. permissions=17600775980032
           discord-application-id: ${{ secrets.DISCORD_APPLICATION_ID }}
           google-calendar-id: ${{ secrets.GOOGLE_CALENDAR_CALENDAR_ID }}
-          google-api-key: ${{ secrets.GOOGLE_CALENDAR_API_KEY }}
+          google-service-account-key-json: ${{ secrets.GOOGLE_CALENDAR_SERVICE_ACCOUNT_KEY_JSON }} # either use google-api-key or google-service-account-key-json
+          google-api-key: ${{ secrets.GOOGLE_CALENDAR_API_KEY }} # either use google-api-key or google-service-account-key-json
 ```
 
 ## How does it work?
@@ -47,3 +48,14 @@ variables or in `.env.` file in the root of the repository.
 ## Discord bot permissions
 
 The Discord bot needs "Read Messages/View Channels", "Manage Events" permissions.
+
+## Google Cloud setup
+
+1. Enable the Google Calendar API for the Google Cloud project.
+2. Create a service account and download the JSON key.
+   1. Credeintials -> Create Credentials -> Service Account -> JSON key
+   2. In Step 2 (Grant this service account access to project): Add "Service Account Token Creator" role
+   3. After creation, click on the service account, go to "Keys" tab, and create a new JSON key.
+   4. Save the JSON key as a secret in the GitHub repository.
+3. Share the Google Calendar with the service account email. "Settings and sharing" -> "Share with specific people" ->
+   Add the service account email. Give it "See all event details" permission.

action.yml

@@ -28,3 +28,4 @@ runs:
         DISCORD_EVENTS_SYNC_DISCORD_APPLICATION_ID: ${{ inputs.discord-application-id }}
         DISCORD_EVENTS_SYNC_GOOGLE_CALENDAR_CALENDAR_ID: ${{ inputs.google-calendar-id }}
         DISCORD_EVENTS_SYNC_GOOGLE_CALENDAR_API_KEY: ${{ inputs.google-api-key }}
+        DISCORD_EVENTS_SYNC_GOOGLE_CALENDAR_SERVICE_ACCOUNT_KEY_JSON: ${{ inputs.google-service-account-key-json }}

envConfig.ts

@@ -3,29 +3,43 @@ import "@std/dotenv/load";
 /** Prefix used for environment variable config options */
 const ENVIRONMENT_VARIABLE_PREFIX = "DISCORD_EVENTS_SYNC_";
 
-const getEnv = (name: string) => {
+const getEnv = (name: string, required: boolean = true) => {
   const envName = ENVIRONMENT_VARIABLE_PREFIX + name;
   const value = Deno.env.get(envName);
   if (value) {
     return value;
   }
-
-  const message = `Environment {${envName}} not found.`;
-  console.error(message);
-  throw new Error(message);
+  if (required) {
+    const message = `Environment {${envName}} not found.`;
+    throw new Error(message);
+  }
 };
 
 export const loadEnvConfig = () => {
+  const serviceAccountKeyJson = getEnv(
+    "GOOGLE_CALENDAR_SERVICE_ACCOUNT_KEY_JSON",
+    false,
+  );
+
+  const apiKey = getEnv("GOOGLE_CALENDAR_API_KEY", false);
+
+  if (!serviceAccountKeyJson && !apiKey) {
+    throw new Error(
+      `Either {${ENVIRONMENT_VARIABLE_PREFIX}GOOGLE_CALENDAR_SERVICE_ACCOUNT_KEY_JSON} or {${ENVIRONMENT_VARIABLE_PREFIX}GOOGLE_CALENDAR_API_KEY} must be provided.`,
+    );
+  }
+
   const config = {
     discord: {
-      guildId: getEnv("DISCORD_GUILD_ID"),
-      botToken: getEnv("DISCORD_BOT_TOKEN"),
-      applicationId: getEnv("DISCORD_APPLICATION_ID"),
+      guildId: getEnv("DISCORD_GUILD_ID")!,
+      botToken: getEnv("DISCORD_BOT_TOKEN")!,
+      applicationId: getEnv("DISCORD_APPLICATION_ID")!,
     },
     googleCalendar: {
-      calendarId: getEnv("GOOGLE_CALENDAR_CALENDAR_ID"),
-      apiKey: getEnv("GOOGLE_CALENDAR_API_KEY"),
+      calendarId: getEnv("GOOGLE_CALENDAR_CALENDAR_ID")!,
+      ...(serviceAccountKeyJson ? { serviceAccountKeyJson: serviceAccountKeyJson! } : { apiKey: apiKey! }),
     },
   };
+
   return config;
 };

gcal.ts

@@ -15,38 +15,151 @@ export interface IGetCalendarEventsParams {
 
 export class GoogleCalendarClient {
   #calendarId: string;
-  #apiKey: string;
+  #apiKey: string | undefined;
+  #serviceAccountKeyJson:
+    | {
+      private_key: string;
+      client_email: string;
+    }
+    | undefined;
 
-  constructor({ calendarId, apiKey }: { calendarId: string; apiKey: string }) {
-    this.#calendarId = calendarId;
-    this.#apiKey = apiKey;
+  constructor(
+    options:
+      | { calendarId: string; apiKey: string }
+      | {
+        calendarId: string;
+        serviceAccountKeyJson: string;
+      },
+  ) {
+    if ("serviceAccountKeyJson" in options) {
+      const { calendarId, serviceAccountKeyJson } = options;
+      this.#calendarId = calendarId;
+      this.#serviceAccountKeyJson = JSON.parse(serviceAccountKeyJson);
+    } else {
+      const { calendarId, apiKey } = options;
+      this.#calendarId = calendarId;
+      this.#apiKey = apiKey;
+    }
   }
 
-  public async getEvents(
-    { singleEvents, timeMax, timeMin, maxResults, orderBy }: IGetCalendarEventsParams,
-  ) {
+  private async getAccessToken() {
+    if (!this.#serviceAccountKeyJson) {
+      throw new Error("Service Account Key JSON not provided.");
+    }
+
+    const { client_email, private_key } = this.#serviceAccountKeyJson;
+    console.log(`Getting access token for ${client_email}`);
+
+    const header = { alg: "RS256", typ: "JWT" };
+    const now = Math.floor(Date.now() / 1000);
+    const claims = {
+      iss: client_email,
+      scope: "https://www.googleapis.com/auth/calendar.events.readonly",
+      aud: "https://oauth2.googleapis.com/token",
+      iat: now,
+      exp: now + 3600,
+    };
+
+    const encodeBase64Url = (data: string): string => {
+      return btoa(data)
+        .replace(/\+/g, "-")
+        .replace(/\//g, "_")
+        .replace(/=+$/, "");
+    };
+    const base64UrlHeader = encodeBase64Url(JSON.stringify(header));
+    const base64UrlClaims = encodeBase64Url(JSON.stringify(claims));
+    const unsignedJwt = `${base64UrlHeader}.${base64UrlClaims}`;
+
+    const b64 = private_key
+      .replace(/-----\w+ PRIVATE KEY-----/g, "")
+      .replace(/\n/g, "");
+    const binary = atob(b64);
+    const buffer = new ArrayBuffer(binary.length);
+    const view = new Uint8Array(buffer);
+    for (let i = 0; i < binary.length; i++) {
+      view[i] = binary.charCodeAt(i);
+    }
+    const cryptoKey = await crypto.subtle.importKey(
+      "pkcs8",
+      buffer,
+      { name: "RSASSA-PKCS1-v1_5", hash: "SHA-256" },
+      false,
+      ["sign"],
+    );
+    const signature = await crypto.subtle.sign(
+      "RSASSA-PKCS1-v1_5",
+      cryptoKey,
+      new TextEncoder().encode(unsignedJwt),
+    );
+    const signedJwt = `${unsignedJwt}.${
+      encodeBase64Url(
+        new Uint8Array(signature).reduce(
+          (str, byte) => str + String.fromCharCode(byte),
+          "",
+        ),
+      )
+    }`;
+
+    const response = await fetch("https://oauth2.googleapis.com/token", {
+      method: "POST",
+      headers: { "Content-Type": "application/x-www-form-urlencoded" },
+      body: new URLSearchParams({
+        grant_type: "urn:ietf:params:oauth:grant-type:jwt-bearer",
+        assertion: signedJwt,
+      }),
+    });
+
+    const tokenResponse = await response.json();
+    return tokenResponse as {
+      access_token: string;
+      expires_in: number;
+      token_type: string;
+    };
+  }
+
+  public async getEvents({
+    singleEvents,
+    timeMax,
+    timeMin,
+    maxResults,
+    orderBy,
+  }: IGetCalendarEventsParams) {
     try {
-      const calendarRequestParams = {
+      const calendarRequestParams: Record<string, string> = {
         singleEvents: singleEvents.toString(),
         timeMin: timeMin.toISOString(),
         timeMax: timeMax.toISOString(),
         maxResults: `${maxResults}`,
         orderBy,
-        key: this.#apiKey,
       };
+
+      const calendarRequestHeaders: Record<string, string> = {
+        Referer: "discord-events-sync",
+      };
+
+      if (this.#serviceAccountKeyJson) {
+        const accessToken = await this.getAccessToken();
+        calendarRequestHeaders[
+          "Authorization"
+        ] = `${accessToken.token_type} ${accessToken.access_token}`;
+      } else if (this.#apiKey) {
+        calendarRequestParams["key"] = this.#apiKey;
+      }
+
       const calendarResponse = await fetch(
-        `${API_BASE_URL}/calendars/${this.#calendarId}/events?${
-          (new URLSearchParams(calendarRequestParams)).toString()
-        }`,
-        { headers: { Referer: "discord-events-sync" } },
+        `${API_BASE_URL}/calendars/${this.#calendarId}/events?${new URLSearchParams(calendarRequestParams).toString()}`,
+        { headers: calendarRequestHeaders },
       );
+      if (!calendarResponse.ok) {
+        throw new Error(
+          `Error getting events from Google Calendar API. Status: ${calendarResponse.status}. Response: ${await calendarResponse
+            .text()}`,
+        );
+      }
       const parsed = await calendarResponse.json();
-
       return parsed;
     } catch (e) {
-      console.error(
-        `Error getting events from Google Calendar API.`,
-      );
+      console.error(`Error getting events from Google Calendar API.`);
       throw e;
     }
   }